The +10 diopter lens occluder

Background It would be useful to be able to visualize the eye under cover during the cover test. Used as an occluder, a +10 diopter (D) lens will permit such visualization. It is important to know if a +10D lens creates dissociation that is qualitatively similar to an opaque occluder. Methods The angle of strabismus was measured in 33 patients with esotropia. Seventeen had intermittent exotropia, and 15 had dissociated vertical divergence with both an opaque occluder and a +10D lens used as an occluder. The findings were then compared. Results In 64 of the 65 patients participating in this study, the measurements obtained with the 2 occluders agreed within 3 prism diopters on repeated testing. In the remaining patient, the measurements differed by 5 prism diopters. In all patients, the dissociated eye could be clearly visualized through the +10D lens. Conclusion A +10D lens permits excellent visualization of the dissociated eye and provides measurements that are qualitatively similar to those obtained with a standard occluder.